Speakers
Description
The Muon g-2 experiment at Fermilab aims to measure the muon anomalous magnetic moment
($a_{\mu}$) with a final accuracy of 140 part per billions (ppb). The first result on Run-1 dataset
were unveiled on April 7, 2021, showing a very good agreement with the previous experimental
result at Brookhaven National Laboratory (BNL), improving the uncertainty by achieving a precision
of 460 ppb compared to 540 ppb of BNL. Due to the extremely high precision of the experiment four
different beam dynamics corrections must be applied to obtain the final value of the anomalous
precession frequency. Two corrections are associated with the use of electrostatic quadrupole (ESQ)
vertical focusing on the storage ring. A vertically magnetic field is felt by muons passing through the
radial electric field components created by the ESQ system. Due to the vertical betatron motions
the muons do not orbit the ring in a plane orthogonal to the vertical magnetic field direction. A
correction is necessary to account for an average pitch angle associated with their trajectories. A
third correction is caused by muons that escape the ring during the storage time experiencing a
biased initial spin phase compared to the parent distribution. Finally, because two high-voltage
resistors in the ESQ network had longer than designed $RC$ time constants, the vertical and
horizontal centroids of the stored muon beam drifted slightly, during each storage ring fill. This led
to the phase-acceptance relationship that requires a correction. I will present this high precision
measurement focusing on the beam dynamics corrections to $\omega_a$.
| First author | G. Venanzoni |
|---|---|
| gvenanzo@cern.ch | |
| Collaboration / Activity | Muon g-2 Collaboration |
